[GRASS-dev] v.out.lidar: export point cloud from GRASS

[Vaclav Petras]

Hi all,

in r66855 I've implemented an export module for LAS files. The main
motivation is creating test data for v.in.lidar and r.in.lidar and
visualization of points in plas.io. Most of the lidar attributes are
supported when provided in attribute table or as categories in separate
layers.

Colors can be also stored in the separate layers as proposed earlier on the
mailing list. There is nothing in GRASS currently which could write it
(I've used modified v.in.lidar) but two options are supported, one color
per layer and RGB as one category (using bit shifts). There is a discussion
for this linked below.

All the layers and columns (one per attribute) are causing quite long
option list. In GUI, it is well separated using guisection but it is a lot
of to fill out anyway. Layers cannot be avoided but perhaps columns can
have some predefined names which would be used with a given flag enabled.

Current limitations: Skipping points without category, color entry in the
attribute table or filtered out by where option is not supported. Some
lidar point attributes are not yet supported. Offsets and scales for
coordinates are not supported. Z coordinate is always expected.

In addition to the color options above, a possible improvement would be
specifying color table for z values as it is implemented in d.vect. This,
however, requires min and max z which are accessible only with topology or
after iterating over all data (well, unless user specifies z range or
something).

Besides the usages mentioned above, it seems that v.out.lidar might be
useful, with certain speed limitations, when using spatial selection in
v.in.lidar or grid-based decimation in v.decimate, but LAS is the desired
output format.

Vaclav


r66855: v.out.lidar: export vector as LAS
https://trac.osgeo.org/grass/changeset/66855

Using layers and categories for something else than ID and class
https://lists.osgeo.org/pipermail/grass-dev/2015-September/076552.html

v.in.lidar: limit the import to a set of polygons
https://lists.osgeo.org/pipermail/grass-dev/2015-November/077311.html

v.in.lidar: decimation (skip, preserve, offset, limit)
https://lists.osgeo.org/pipermail/grass-dev/2015-September/076275.html

v.decimate: point cloud decimation of native vector maps
https://lists.osgeo.org/pipermail/grass-dev/2015-September/076562.html
(not yet enabled in the parent Makefile)
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